Screw-propeller



(No Model.) Y

R. BELL 8a' D. SELKIRK.

SCREW PROPBLLER.

No. 285,212. Patented Sept. 18, 1 883.

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NITED STATES PATENT @Erica RICHARD BELL, OE LIVERPOOL, ENGLAND, AND DAviD sELKiRK, OE BROOKLYN, NEW YORK.

SCREW-PROPELLER.

SPECIFICATION forming part of Letters Patent No. 285,212, dated September 18, 1883.

Application filed September 16, 1852.

of America, respectively, have invented a new and useful Improvement in ScrewPropellers, of which the following is a speciiication.

The object of our invention is to provide a screw-prop eller ofan improved construction by which the water acted on by the blades as theV .propeller revolves will be thrown backward and toward the center of the propeller-shaft, and which will obviate the tendency usual in propellers as hitherto constructed to carry the water around with the blades, and thus will act with greater efficiency ofpropulsion and produce less commotion in the water than propellers of former construction.

In the accompanying drawings, Figure l represents an end elevation, showing the rear surface of a screw-propeller constructed according to our present invention. Fig. 2 is an edge view of the same, (seen in the direction of arrow 1 of Fig. 1,) showing the form of one of the compound blades, Fig. 3 is a vertical section of the same, taken on the line x x of Fig. l, and seen in the direction of arrow 2.

Avis the propeller-hub. B are the blades, or, as we will. here call them, compound blades.77 Each bladeB is composed of asmaller blade, C, forming the forward or cutting edge of the blade B, alarger blade, D, forming the rear or main surface, and one or more or. a series of cross-blades, E, uniting the front and rear portion, C D, of the compound blade B, and leaving openings F between each other and the said portion C D. The terms front 7 and rear are here used relative to the motion ofthe propeller, which,whenworking, revolves in the direction indicated by arrow?) in Fig. 1. The blades D C have the same pitch and are constructed in the manner as ordinary propellers; but the cross-blades E have, in addition to the helical pitch common to the vblades D C,

a pitch or inclinati-on toward the axis of the propeller'shaft, or, in other words, they are so placed, as shown in Fig. 8, that their workingsurface at any cross-section (e) will lie in a line parallel with the side surface of a cone,

(No model.)

a. b c, having its apex c situated in the axis of the propeller-shaft at a point forward of the propeller. By this construction it is evident that the water cut during the revolution of the propeller by the cross-blades E will be thrown back toward the extended axial line of the propeller-shaft in rear of the propeller, or in the direction of line fg, forming about a right angle with the working-surface of the cross-blades E-at the cross-section c. ln order not to cut through the water in the same plane at the same time, the outer cross-blades are set alit tle in rear of the inner ones, or so that the line and shaft of the propeller, but are spiral or eccentric thereto; or, in other words, they are circle arcs whose center M lies outside of the center of the propeller in such a position that the radial distance from the center of the propeller-shaft to the forward end of each cross blade is greater than the radial distance from the same center to the rear end of the saine cross-blades. This causes the cross-blades to make a slantin g cut through the water, and allows the large blade D to act upon a column of water glancing off from the cross-blades, centralized or solidied, as it were, by them. Vith reference to Fig. l this will be clear.

For instance, the curve m a of a cross-blade,

and as the propeller revolves in direction of 9o arrow 3, a portion of the outer end, d, of the large blade D, at a distance radially beyond the rear end of the cross-blade, intercepts the said arcjk. The combined action ofthe helical cut of the bladeD and the additional conically helical and spiral cut of the cross-blades E not only prevents the water from moving around with and from being thrown out laterally by the blades, but compresses it centrally rearward, thereby increasing the effect of propul IOO 2 v essere sion ofthe vessel, or, as it is technically termed, the propeller makes solid Water,77 and consequently more thrust XVe depend for effect on the cross-blades E and the large blade D, the smaller blade C serving the purpose, mainly, of strengthening the cross-blades, which otherwise might be broken by striking against accidental obstruction. In the absence of any obstructions the blade Gmight just aswell be entirely dispensed with. Any number of blades and cross-blades may be used, and the whole propeller may be either cast in one solid piece or composed of separate pieces.

Having thus described our invention, We claim as new and desire to secure by Letters Patent- Y l. A propeller-blade formed of a radial blade, D, having helical pitch, and of one or more cross-blades, E, having a helical and also a conical pitch, and emanating from the radial blades, substantially as speciiied.

2. A propeller-blade formed oi" a radial blade, D, having helical pitch, and of one or more crossblades, E, emanating from the ra- 25 dial blades, said cross-blades having a helical and also a conical pitch and a spiral location by being curved on a center, M, situated outside of the propeller center, substantially as specified.

8. A propeller-blade formed of a radial blade, D, having helical pitch, and of crossblades E, having a helical and also a conical pitch, and emanating from the radial blades, said cross-blades being situated in different planes of axial cross-sections, as Well as at different radial distances from the propeller center, substantially as hereinbefore set forth,

In testimony that We claim the foregoing as our invention We have signed'our names, in Y4o presence of two Witnesses, this 21st day of August, 1882.

RICHARD BELL.

DAVID SELKIRK.

X'Vitnesses:

A. W. ALMQvIs'r, FRaNers C. BOWEN. 

